Liquid Sequence for Stiction-Free Drying of High-Aspect Ratio Features
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Solution Overview
Problem
In semiconductor device fabrication, the drying process after cleaning can cause stiction issues due to capillary forces, especially with high-aspect ratio features, and existing solutions like supercritical fluid drying or hydrophobic layer formation are either costly or complex.
Innovation Solution
A method involving a sequence of liquids where the first liquid is miscible with the rinsing liquid and the last liquid makes a contact angle of about 90° with the surface, ensuring the structure remains covered until the last liquid is exposed, preventing stiction by gradual replacement and minimizing contact with air during drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rinsing liquid comprising water is used for cleaning the structure, then cleaning effectiveness is improved, but stiction occurs during drying due to capillary forces
Solution Approach 1:
The patent changes the physical-chemical parameters of the liquid by using a sequence of liquids with progressively changing properties. The sequence transitions from water-miscible liquids to a final liquid with specific contact angle properties (about 90°), thereby changing the surface tension and wetting characteristics to eliminate capillary forces during drying while maintaining cleaning effectiveness.
Solution Approach 2:
The patent introduces intermediate liquids that serve as mediators between water and the final drying liquid. These intermediate liquids are miscible with both water and the final liquid, creating a gradual transition that prevents sudden surface tension changes and capillary forces that would cause stiction, while still allowing effective cleaning to occur.
2Object-affected harmful factors
If supercritical fluid drying is used to prevent stiction, then stiction is avoided, but high pressure systems are required which increase system complexity and cost
Solution Approach 1:
The patent uses a sequence of expendable liquids that can be easily applied and removed without requiring complex equipment. Instead of investing in expensive supercritical fluid systems, the method uses simple liquid sequences that flow through the structure and are discarded, achieving the same stiction-prevention effect with minimal infrastructure.
Solution Approach 2:
The patent replaces the mechanical high-pressure system required for supercritical fluid drying with a chemical solution approach. By using a sequence of liquids with specific miscibility and contact angle properties, the method achieves stiction prevention through chemical surface interactions rather than mechanical pressure application.
3Object-affected harmful factors
If a hydrophobic layer is formed on the sidewalls to prevent stiction, then stiction is avoided, but additional process steps are required which increase manufacturing complexity
Solution Approach 1:
The patent merges the cleaning process with the stiction-prevention process by using a sequence of liquids that performs both functions. The same liquid sequence that cleans the structure also modifies the surface properties to prevent stiction, eliminating the need for separate hydrophobic layer formation steps and reducing overall manufacturing complexity.
Solution Approach 2:
The liquid sequence serves multiple functions: it cleans the structure by removing contaminants, gradually transitions surface properties to prevent capillary forces, and provides stiction protection during drying. This multi-functional approach eliminates the need for separate specialized steps for each function, simplifying the manufacturing process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for effective wet treatment and drying of high-aspect ratio features without the need for high-pressure systems or hydrophobic layer formation, reducing manufacturing costs and preventing stiction, thus enhancing the reliability and efficiency of the semiconductor fabrication process.
Implementation Method 1
a last liquid of the sequence makes a contact angle of about 90° with the second surface and the sidewall
Implementation Method 2
a first liquid of the sequence is miscible with the rinsing liquid and a last liquid of the sequence makes a contact angle of about 90° with the second surface and the sidewall, wherein each of the liquids in the sequence is miscible with the preceding one
Implementation Method 3
The capillary forces of the liquid cause these high-aspect ratio structures to bend and stick to each other during the drying step
Data Source
Figure 1a~1b
Figure 1c~2b
Figure 3a~4b
AI summary
A method for performing a wet treatment of a structure, the method comprising obtaining a structure comprising a first surface comprising a feature fixed at least at a first end to the first surface from which it protrudes, wherein a sidewall of the feature faces and is positioned away from a second surface by a gap g, performing a wet treatment of the structure and subsequently, drying the structure, wherein performing the wet treatment comprises rinsing the structure by exposing it to a rinsing liquid comprising water, and exposing the structure, subsequently, to a sequence of liquids, wherein a first liquid of the sequence is miscible with the rinsing liquid and a last liquid of the sequence makes a contact angle of about 90° with the second surface and the sidewall, wherein each of the liquids in the sequence is miscible with the preceding one, and whereby at least the first surface of the structure remains covered with the rinsing liquid until exposure to the sequence and with each liquid of the sequence until exposure to a subsequent liquid in the sequence.